Stress relaxation electronic part, stress relaxation wiring board, and stress relaxation electronic part mounted body

ABSTRACT

A stress relaxation type electronic component which is to be mounted on a circuit board, wherein a stress relaxation mechanism member is disposed on a surface of said electronic component, said surface being on a side of a connection portion where said electronic component is to be connected to said circuit board, and said stress relaxation mechanism member is electrically conductive.

TECHNICAL FIELD

The present invention relates to an electronic component such as asemiconductor device, a circuit board for mounting such an electroniccomponent, and the like.

BACKGROUND ART

Conventionally, a plastic QFP (Quad Flat Package) in which input/outputlead wires are drawn out from four side faces of a package is often usedas a package type semiconductor device. As large scale integration of anelectronic component such as a semiconductor device advances inaccordance with increase of functions and enhancement of performance ofan electronic apparatus in various fields, the number of input/outputterminals is increased and this increase inevitably causes also thepackage shape of a QFP to expand. In order to solve this problem, thedesign rule of a semiconductor chip is set to a very fine level, and thelead pitch is narrowed, so that requests for miniaturization andthinning of electronic apparatuses of various kinds are satisfied.

In an LSI of a scale of 400 pins or more, however, even when the pitchis narrowed, such requests cannot be sufficiently fulfilled because of,for example, a problem in mass productivity of soldering. Moreover,there is a problem which inevitably arises in the case where anelectronic component such as a semiconductor device package is mountedon a circuit board. Namely, this problem is caused by a difference incoefficient of thermal expansion between the electronic component andthe circuit board. It is very difficult to connect with high reliabilitymany input/output leads of an electronic component to a large number ofelectrode terminals on a circuit board having a coefficient of thermalexpansion which is different from that of the electronic component.Furthermore, input/output leads which are prolonged as a result ofenlargement of a plastic QFP cause a problem in that the signaltransmission rate is lowered.

In order to solve many such problems involved in a plastic QFP,recently, attention is given to a semiconductor device which, unlike aQFP, has no lead pin, such as a BGA (Ball Grid Array) in which sphericalconnection terminals are arranged in a two-dimensional array-like manneron the rear face of a semiconductor device package, or an LGA (Land GridArray) or CSP (Chip Size Package) in which many flat electrodes arearranged in an array-like manner on the rear face of a semiconductordevice package.

In such a semiconductor device, external connection electrodes of a chipcarrier are arranged in a lattice-like manner on the rear face of thechip carrier. Therefore, the semiconductor device can be miniaturized,so that a larger number of electronic components and the like can bemounted in a high density. Consequently, such a semiconductor device canlargely contribute also to a miniaturized electronic apparatus. Sincesuch a semiconductor device has no lead, connections between thesemiconductor device and a circuit board can be shortened and hence thesignal processing rate can be improved.

However, even a BGA of the prior art having such a structure cannotsolve the problems of destruction of a package and a connection failurewhich are caused by a difference in coefficient of thermal expansionwhen the package is mounted on a circuit board and then solderedthereto. Furthermore, a BGA has a problem in that it cannot withstandreliability tests such as a thermal shock test. For example, thecoefficient of thermal expansion of a chip carrier which is mainly madeof ceramics is largely different from that of a circuit board whichconsists of glass fibers and a resin. Therefore, a great stress isgenerated in the connection portion and the reliability of theconnection is lowered.

FIG. 15 shows a connection structure in the prior art in the case wherean electronic component such as a semiconductor device is to beconnected to a circuit board. Electrodes 4 of an electronic component 3in which an LSI chip 1 is mounted on a ceramic carrier 2 are connectedto electrodes 6 of a circuit board 5 by means of solder 7. In thisconnection structure, the coefficient of thermal expansion of theceramic carrier 2 of the electronic component 3 is largely differentfrom that of the circuit board 5 which is made of a synthetic resin,etc. As the dimension L of the electronic component 3 is larger,therefore, a great stress is generated in the connection portion and adanger of destroying the connection portion is increased. Consequently,materials which can be used in an electronic component or a circuitboard are largely restricted.

This will be described more specifically. Generally, the materialconstituting the ceramic carrier 2 on which the LSI chip 1 is mounted islargely different from that constituting the circuit board 5, and hencetheir coefficients of thermal expansion greatly differ from each other.Glass-epoxy resin which is often used as the circuit board 5 has acoefficient of thermal expansion of about 15×10⁻⁶. By contrast, thecoefficient of thermal expansion of the whole of the package of theceramic carrier 2 including the LSI chip 1 is about 2 to 5×10⁻⁶. Whenthe electronic component or an MCM has a size of 30 mm square, in thecase of a temperature difference of 200° C., a dimensional difference ofseveral tens of midrometers is generated in the connection portionbetween the electronic component and the circuit board as compared withthe case of ordinary temperature. A stress due to the difference causesthe connection portion and a weak portion of wiring conductors to bedestroyed.

DISCLOSURE OF INVENTION

The invention has been conducted in order to solve the problems of theprior art. It is an object of the invention to provide a stressrelaxation type electronic component, a stress relaxation type circuitboard, and a stress relaxation type electronic component mounted memberin which destruction of a package or a connection portion due to adifference in coefficient of thermal expansion between an electroniccomponent such as an LSI chip or a semiconductor device package and acircuit board can be prevented from occurring.

According to the invention, in an electronic component which is to bemounted on a circuit board, a stress relaxation mechanism member isdisposed on a surface of the electronic component, the surface being ona side of a connection portion where the electronic component is to beconnected to the circuit board. The invention has a function that,during a thermal shock test, a stress generated owing to a difference incoefficient of thermal expansion is absorbed by the stress relaxationmechanism member. Therefore, a semiconductor device itself or a portionsuch as a connection portion between the semiconductor device and thecircuit board is prevented from being destroyed, and the reliability ofthe connection of the semiconductor device and an electronic apparatuscan be improved.

In the invention, a solderable layer is on a surface on a side where thestress relaxation mechanism member is connected to the circuit board. Itis possible to improve the reliability of the connection of the circuitboard and the electronic component.

In the invention, the solderable layer consists of copper foil, or ametal which is formed by thermally decomposing an organometallic complexfilm. It is possible to produce at a low cost an electronic componenthaving excellent reliability in connection.

In the invention, the stress relaxation mechanism member is formed by anelectrically conductive adhesive agent. The electronic component can beproduced by a relatively simple method and at a low cost.

In the invention, the stress relaxation mechanism member is formed by asolderable electrically conductive adhesive agent. It is possible toprovide at a low cost an electronic component in which the solderabilityand the electrical conductivity can be improved, and which has excellentreliability in connection.

In the invention, the stress relaxation mechanism member is configuredby an electrode which is previously formed on the electronic component.It is possible to produce an electrode having a stress relaxationmechanism member.

The invention is further characterized in that the electrode is made ofan electrically conductive resin composition. It is possible to produceat a relatively low cost an electrode having a stress relaxationmechanism member.

In the invention, the electrically conductive resin compositioncontains, as main components, an electrically conductive filler, athermosetting resin, and expandable hollow synthetic resin particles.The stress relaxation mechanism member is provided by forming an elasticball-like hollow portion inside the electrically conductive resincomposition.

In the invention, an electrically conductive adhesive agent for forminga stress relaxation mechanism member is further formed on an upper faceof the electrode. The stress relaxation function can be exerted moreeffectively.

Another embodiment of the invention is characterized in that, in acircuit board on which an electronic component is to be mounted,a stressrelaxation mechanism member is disposed on a surface of the circuitboard on which the electronic component is to be mounted. The inventionhas a function that, during a thermal shock test, a stress generatedowing to a difference in coefficient of thermal expansion is absorbed bythe stress relaxation mechanism member. Therefore, a semiconductordevice itself or a connection portion between the semiconductor deviceand the circuit board is prevented from being destroyed, and thereliability of the semiconductor device and an electronic apparatus canbe improved.

Another embodiment is characterized in that, in a circuit board on whichplural electronic components are to be mounted, a stress relaxationmechanism member is previously disposed on a surface portion of thecircuit board on which the electronic components, are to be mounted.Even when plural electronic components having any coefficient of thermalexpansion are mounted on the circuit board, it is possible to maintainhigh reliability in connection.

Yet another embodiment is characterized in that the plural electroniccomponents have different sizes or different shapes. Even whenelectronic components which are to be mounted have any dimension andshape, it is possible to mount the electronic components by whilemaintaining excellent reliability in connection.

In the invention, the stress relaxation mechanism member is configuredby a layer which can be soldered to a surface on the side where theelectronic component is to be mounted. It is possible to improve thereliability of connection of the circuit board and the electroniccomponent.

In the invention, the, solderable layer consists of copper foil, or ametal which is formed by thermally decomposing an organometallic complexfilm. It is possible to provide at a low cost an electroinic componentwhich has excellent reliability in connection.

In the invention, the stress relaxation mechanism member is formed by anelectrically conductive adhesive agent. The circuit board can beproduced by a relatively simple method and at a low cost.

In the invention, the stress relaxation mechanism member is formed by asolderable electrically conductive adhesive agent. It is possible toprovide at a low cost an electronic component in which the solderabityand the electrical conductivity can be improved, and which has excellentreliability in connection.

In the invention, the stress relaxation mechanism member is configuredby an electrode which is previously formed on the circuit board. It ispossible to produce an electrode having a stress relaxation mechanism.

The invention is further characterized in that the electrode isconfigured by of an electrically conductive resin composition. Anelectrode having a stress relaxation mechanism can be produced by asimple process.

In the invention, the electrically conductive resin compositioncontains, as main components, at least an electrically conductivefiller, a thermosetting resin, and expandable hollow synthetic resinparticles. The stress relaxation mechanism member is provided by formingan elastic ball-like hollow portion inside the electrically conductiveresin composition.

The invention is further characterized in that an electricallyconductive adhesive agent for forming a stress relaxation mechanismmember is further formed on an upper face of the electrode. The stressrelaxation function can be exerted more effectively. In place of such astress relaxation mechanism member, a solder layer may be formed on theupper face of the electrode. In this case, a subsequent repair work canbe easily conducted.

The invention is further characterized in that an electronic componentis mounted on a circuit board via a stress relaxation mechanism member.It is possible to provide an electronic component mounted member whichcan be applied to an electronic apparatus that will be used in severeenvironmental conditions.

The invention is further characterized in that the stress relaxationmechanism member is formed by an electrically conductive adhesive agentand a solder layer. An electronic component mounted member having astress relaxation function can be formed by a relatively easy processand at a lower cost.

The invention is further characterized in that the stress relaxationmechanism member functions also as an electrode. An electrode having astress relaxation mechanism can be easily produced.

The invention is further characterized in that the stress relaxationmechanism member is configured by an electrode made of an electricallyconductive resin composition disposed on the electronic component and/orthe circuit board, and at least one of an electrically conductiveadhesive agent and a solder layer. It is possible to improve thereliability of connection of the electronic component mounted member.

The invention is further;characterized in that the electronic componentconsists of plural electronic components having different sizes ordifferent shapes. Even when electronic components which are to bemounted have any dimension and shape, it is possible in any case toobtain an electronic component mounted member which has excellentreliability in connection.

The invention is further characterized in that the electricallyconductive adhesive agent and the solder layer are connected to eachother via a solderable layer. When an electronic component is mounted ona circuit board, it is possible to attain excellent solderability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of a stress relaxation type electroniccomponent of a first embodiment of the invention.

FIG. 2 is a section view of a stress relaxation type electroniccomponent of a second embodiment of the invention.

FIG. 3 is a section view of a solderable electrically conductiveadhesive agent in the embodiment.

FIG. 4 is a section view of a stress relaxation type electroniccomponent of a third embodiment of the invention.

FIG. 5 is a section view of a stress relaxation type electroniccomponent of a fourth embodiment of the invention.

FIG. 6 is a section view of a stress relaxation type circuit board of afifth embodiment of the invention.

FIG. 7 is a section view of a stress relaxation type circuit board ofanother example of the fifth embodiment.

FIGS. 8(a) and 8(b) are section views of a stress relaxation typecircuit board of a sixth embodiment of the invention.

FIG. 9 is a section view of a stress relaxation type circuit board of aseventh embodiment of the invention.

FIG. 10 is a section view of a stress relaxation type circuit board ofan eighth embodiment of the invention.

FIGS. 11(a) and 11(b) are section views of a stress relaxation typeelectronic component mounted member of a ninth embodiment of theinvention.

FIG. 12 is a section view of a stress relaxation type electroniccomponent mounted member of a tenth embodiment of the invention.

FIG. 13 is a section view of a stress relaxation type electroniccomponent mounted member of an eleventh embodiment of the invention.

FIG. 14 is a partial enlarged section view of a stress relaxation typeelectronic component mounted member of a twelfth embodiment of theinvention.

FIG. 15 is a section view of an electronic component mounted member ofthe prior art.

LEGEND OF THE REFERENCE NUMERALS

11 LSI chip 12 ceramic carrier 13 electronic component 14, 19, 22, 35electrode 15, 19, 20, 24 stress relaxation mechanism member 15electrically conductive paste 16, 31 solderable layer 21, 27, 28, 34circuit board 25, 26 connection portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of the stress relaxation type electroniccomponent of the invention will be described with reference to theaccompanying drawings.

FIG. 1 shows the configuration of a stress relaxation type electroniccomponent of the first embodiment of the invention. Electrodes 14 whichare to be connected to a circuit board are disposed on the lower face ofan electronic component 13 consisting of a ceramic carrier 12 on whichan LSI chip 11 is to be mounted. The reference numeral 15 denotes astress relaxation mechanism member which is formed by an electricallyconductive adhesive agent consisting of a mixture of an electricallyconductive filler such as copper powder or silver powder, and asynthetic resin material. The conductive adhesive agent constituting thestress relaxation mechanism member 15 in the embodiment may be anelectrically conductive adhesive agent having a property that solderingcan be directly performed on the surface.

In this way, the stress relaxation mechanism member 15 formed by theconductive adhesive agent is disposed on each of connection portionssuch as the electrodes 14 on the side of the electronic component 13where the component is to be mounted on the circuit board. As a result,a stress which, when the temperature is raised, is generated owing to adifference in coefficient of thermal expansion between the electroniccomponent 13 and the circuit board is absorbed by the elasticity of thestress relaxation mechanism member 15, so that failures such asdestruction of the electronic component, breakage of the connectionportions, or peeling of a wiring conductor from the circuit board areprevented from occurring.

FIG. 3 illustrates in more detail the conductive adhesive agent 15 whichis solderable and which has been described in the first embodiment. As aspecific example of the conductive adhesive agent, S-5000 manufacturedby MITSUI KINZOKU TORYO KAGAKU K.K. will be described. FIG. 3(a) shows apart of the conductive adhesive agent 15 (also referred to as conductivepaste) which is in an uncured state. An electrically conductive filler17 such as copper powder is sealed up in a synthetic resin material 18which is uncured and fluid, so as to be in a nonconductive state. Theconductive adhesive paste 15 is applied to the electrodes 14 as shown inFIG. 1 or 2, and then heat-cured at about 160° C. for 30 minutes,whereby the synthetic resin 18 greatly shrinks, so that the volume ofthe resin becomes smaller than the accumulated volume of the conductivefiller 17. This causes the packing density of the conductive filler 17in the conductive adhesive paste 15 to be extremely increased, wherebyparticles of the conductive filler 17 are strongly contacted with eachother so as to exert electrical conductivity. At the same, as shown inFIG. 3(b), part of the conductive filler 17 is exposed from the curedconductive adhesive paste 15, so that direct soldering is enabled.

Another specific example of the solderable conductive adhesive agent 15is disclosed in Japanese Patent Publication (Kokai) No. SH055-160072.Namely, it is possible to use an electrically conductive adhesive agentmade of: powder of electrolytic copper which is excellent in electricalconductivity and dispersibility; non-eutectic solder powder which is ina semi-molten state at the curing temperature of a resin; athermosetting resin; and an active agent. A further specific example isdisclosed in Japanese Patent Publication (Kokai) No. SH057-113505.Namely, electrically conductive paste in which copper powder the surfaceof which is plated, and solder powder are used as an electricallyconductive filler is used, and a binding resin consisting of an epoxyresin and the like, an active agent, and a solvent are added to thefiller and kneaded.

FIG. 2 shows the configuration of a stress relaxation type electroniccomponent of a second embodiment of the invention. The basicconfiguration of the embodiment is identical with that of the firstembodiment, and hence different points will be described.

In the embodiment, the stress relaxation mechanism member 15 consistingof an electrically conductive adhesive agent is formed on the electrodes14 of the electronic component 13. A solderable layer 16 is separatelydisposed on a surface of the stress relaxation mechanism member 15 onthe side where the component is to be connected to the circuit board. Asthe solderable layer 16, copper foil may be used. Alternatively, as thesolderable layer 16, a deposited metal may be used which is obtained bycontacting a metal complex solution in which a complex of a metal, forexample, Pd, Au, or Pt is dissolved in an organic solvent such astoluene, xylene, or alcohol, with the conductive adhesive agent of thestress relaxation mechanism member 15, and then depositing the metal ohthe contact interface. When such a deposited metal is used, it ispossible to improve reliability of connection. The use of such adeposited metal has another advantage that the pasting of the metalcomplex solution enables the solderable layer 16 to be formed on thesurface of the stress relaxation mechanism member 15 in a relativelyeasy manner by using a conventional printing method.

Next, a third embodiment of the invention will be described. FIG. 4shows the configuration of a stress relaxation type electronic componentof the third embodiment of the invention. The embodiment is identicalwith the first and second embodiments in that the LSI chip 11 is mountedon the ceramic carrier 12 to form the electronic component 13, and isdifferent in that, in the embodiment, electrodes 19 themselves which aredisposed on the side where the electronic component 13 is connected tothe circuit board is configured by a stress relaxation mechanism member.Particularly, the embodiment is characterized in that an electricallyconductive resin composition containing, as main components, anelectrically conductive filler, a thermosetting resin, and expandablehollow synthetic resin particles is used as a material constituting thestress relaxation mechanism member 19.

Next, a fourth embodiment of the invention will be described. FIG. 5shows the configuration of a stress relaxation type electronic componentof the fourth embodiment of the invention. The stress relaxation typeelectronic component of the embodiment is different from the thirdembodiment in that a stress relaxation mechanism member 20 made of anelectrically conductive adhesive agent is further formed on the upperface of each of the electrodes 19 which are stress relaxation mechanismmembers disposed on the electronic component 13. According to thisconfiguration, the connection portion between the electronic component13 and the circuit board is provided with a double stress relaxationmechanism, and hence reliability of connection is further improved.

Next, a stress relaxation circuit board of a fifth embodiment of theinvention will be described with reference to the accompanying drawings.FIG. 6 shows the configuration of a stress relaxation type circuit boardof the fifth embodiment of the invention. As shown in the figure,electrodes 22 which, when an electronic component is mounted, are to beconnected to electrodes of the electronic component, and wirings 23 forforming electronic circuits are formed on the upper face of the circuitboard 21. A stress relaxation mechanism member 24 which is made of anelectrically conductive adhesive agent or an electrically conductiveadhesive agent that is solderable is disposed on the surface of each ofthe electrodes 22. In this way, a stress relaxation mechanism member 24made of the electrically conductive adhesive agent is disposed in aconnection portion such as the electrode 22, on the side of the circuitboard 21 where the electronic component is to be mounted. As a result, astress which, when the temperature is raised, is generated owing to adifference in coefficient of thermal expansion between the electroniccomponent and the circuit board 21 is absorbed by the elasticity of thestress relaxation mechanism member 24, so that failures such asdestruction of the electronic component, breakage of the connectionportions, or peeling of a wiring conductor from the circuit board 21 areprevented from occurring.

FIG. 7 is a section view of a stress relaxation circuit board 27 onwhich plural electronic components having different sizes or differentshapes, for example, a logic LSI and a memory chip. The circuit board 27comprises connection portions 25 and 26 for mounting and connectingplural electronic components. Each of the connection portions 25 isconfigured by an electrode 25 a and a stress relaxation mechanism member25 b, and each of the connection portions 26 by an electrode 26 a and astress relaxation mechanism member 26 b. Even when a large number ofhigh function semiconductor devices having a large size, large activecircuit components such as MCMs (Multi-Chip Modules) on which pluralsemiconductor chips are mounted, small passive circuit componentstypified by cylindrical chip resistors and chip capacitors, and the likeare mounted, therefore, the circuit board of the embodiment can attainhigh reliability of connection.

Next, a stress relaxation circuit board of a sixth embodiment of theinvention will be described. FIG. 8(a) shows a stress relaxation typecircuit board on which a single electronic component is to be mounted,and FIG. 8(b) shows a stress relaxation type circuit board on whichplural electronic components are to be mounted. The basic configurationof the embodiment is identical with that of the fifth embodiment, andhence different points will be described.

In the embodiment, a stress relaxation mechanism member 30 consisting ofan electrically conductive adhesive agent is formed on electrodes 29 ofa circuit board 28. A solderable layer 31 is separately disposed on asurface of the stress relaxation mechanism member 30 on the side wherethe member is to be connected to the electronic component. In the samemanner as the stress relaxation type electronic component of the secondembodiment of the invention, copper foil may be used as the solderablelayer 31. Alternatively, as the solderable layer 31, a deposited metalmay be used which is obtained by contacting a metal complex solution inwhich a complex of a metal, for example, Pd, Au, or Pt is dissolved inan organic solvent such as toluene, xylene, or alcohol, with theconductive adhesive agent of the stress relaxation mechanism member 30,and then depositing the metal on the contact interface. When such adeposited metal is used, it is possible to improve reliability ofconnection. It is a matter of course that the same configuration may beemployed also in the case of FIG. 8(b) in which plural electroniccomponents are mounted.

Next, a stress relaxation circuit board of a seventh embodiment of theinvention will be described with reference to FIG. 9.

Also in the embodiment, a single electronic component or pluralelectronic components may be mounted. However, the figure shows only anexample in which plural electronic components are mounted. FIG. 9 showsa section of the stress relaxation type circuit board of the embodiment.In the embodiment, each electrode 33 itself which is on a circuit board32 and to be connected to an electronic component is configured by astress relaxation mechanism member. Particularly, an electricallyconductive resin composition containing, as main components, anelectrically conductive filler, a thermosetting resin, and expandablehollow synthetic resin particles is used as a material constituting thestress relaxation mechanism member 32.

Next, a stress relaxation circuit board of an eighth embodiment of theinvention will be described with reference to FIG. 10. The embodiment isdifferent from the seventh embodiment in that a further electricallyconductive adhesive agent or a solder layer 36 is disposed on the upperface of each electrode 35 which is disposed on a circuit board 34 andconfigured by a stress relaxation mechanism member. The existence of thestress relaxation mechanism member can improve reliability of connectionwith an electronic component, and that of the solder layer enables arepair work to be easily conducted.

Next, a stress relaxation type electronic component mounted member of aninth embodiment of the invention will be described. FIGS. 11(a) and11(b) are section views showing the structure of the stress relaxationtype electronic component mounted member of the ninth embodiment onwhich plural electronic components are to be mounted. A connectionportion between a circuit board 37 and an electronic component 40consisting of an LSI chip 38 and a ceramic carrier 39 is configured bytheir electrodes 41 a and 41 b, an electrically conductive adhesiveagent 41 which is a stress relaxation mechanism member sandwichedbetween the electrodes 41 a and 41 b, and a solder layer 42. FIG. 11(a)shows a case where the conductive adhesive agent 41 serving as a stressrelaxation mechanism member is disposed on the upper face of theelectrode 41 a of the circuit board 37, and FIG. 11(b) a case where theconductive adhesive agent 41 serving as a stress relaxation mechanismmember is disposed on the upper face of the electrode 41 b of theelectronic component 40.

FIG. 12 shows the sectional structure of a stress relaxation typeelectronic component mounted member of a tenth embodiment of theinvention. An electrode 45 disposed on a circuit board 43, and a solderlayer 46 are arranged between the circuit board 43 and an electroniccomponent 44. The electrode 45 is made of an electrically conductiveresin composition serving as a stress relaxation mechanism member.

Next, a stress relaxation type electronic component mounted member of aneleventh embodiment of the invention will be described. FIG. 13 is asection view showing the structure of the stress relaxation typeelectronic component mounted member of the eleventh embodiment on whichplural electronic components are to be mounted. In a connection portionbetween a circuit board 47 and an electronic component 50 consisting ofan LSI chip 48 and a ceramic carrier 49, there are an electrode 51 whichis made of an electrically conductive resin composition and disposed onthe circuit board 47, an electrically conductive adhesive agent 52 whichis disposed on the upper face of the electrode, and a solder layer 53which is disposed on the upper face of the conductive adhesive agent.The electrode 51 and the conductive adhesive agent 52 simultaneouslyconstitute a stress relaxation-mechanism member.

Next, a stress relaxation type electronic component mounted member of atwelfth embodiment of the invention will be described. FIG. 14 is anenlarged section view showing a part of the stress relaxation typeelectronic component mounted member of the embodiment. In a connectionportion between an electrode 55 of a circuit board 54 and An electrode59 of an electronic component 58 consisting of an LSI chip 56 and aceramic carrier 57, arranged are an electrically conductive adhesiveagent 60 constituting a stress relaxation mechanism member, a solderablelayer 61, and a solder layer 62.

In the embodiment, a stress generated by a change in the heatenvironment is absorbed by the electrically conductive adhesive aqent 60constituting a stress relaxation mechanism member, or the electroniccomponent 58 and the circuit board 54 are firmly connected to each otherby the solderable layer 61 and the solder layer 62. When the embodimentis employed in an electronic apparatus to be used in severeenvironmental conditions, therefore, it is possible to maintain veryhigh reliability.

Industrial Applicability

As apparent from the above description, according to the invention, in aprocess of soldering an electronic component to a circuit board, athermal shock test on an electronic component mounted member, or thelike, a stress generated owing to a difference in coefficient of thermalexpansion is absorbed by the stress relaxation mechanism member.Therefore, the electronic component itself or a connection portionbetween the electronic component and the circuit board is prevented frombeing destructed, and the reliability of an electronic apparatus can beextremely improved.

What is claimed is:
 1. A stress relaxation type electronic componentwhich is to be mounted on a circuit board, wherein a stress relaxationmechanism member is disposed on a surface of said electronic component,said surface being on a side of a connection portion where saidelectronic component is to be connected to said circuit board, and saidstress relaxation mechanism member is electrically conductive, andwherein a solderable layer is on a surface of said stress relaxationmechanism member, said surface being on a side where said stressrelaxation mechanism member is connected to said circuit board.
 2. Astress relaxation type electronic component according to claim 1,wherein said stress relaxation mechanism member is disposed for each ofelectrodes which are on said connection portion-side surface of saidelectronic component, in a manner that said stress relaxation mechanismmembers are electrically separated from each other.
 3. A stressrelaxation type electronic component according to claim 1 or 2, whereinsaid solderable layer consists of copper foil, or a metal which isformed by thermally discomposing organometallic complex film.
 4. Astress relaxation type electronic component according to claim 1 or 2,wherein said stress relaxation mechanism member is formed by anelectrically conductive adhesive agent.
 5. A stress relaxation typeelectronic component according to claim 1 or 2, wherein said stressrelaxation mechanism member is formed by a solderable electricallyconductive adhesive agent.
 6. A stress relaxation type electroniccomponent according to claim 1, wherein an electrode on said connectionportion-side surface functions also as said stress relaxation mechanismmember.
 7. A stress relaxation type electronic component according toclaim 6, wherein said electrode is made of an electrically conductiveresin composition.
 8. A stress relaxation type electronic componentaccording to claim 7, wherein said electrically conductive resincomposition contains, as main components, at least an electricallyconductive filler, a thermosetting resin, and expandable hollowsynthetic resin particles.
 9. A stress relaxation type electroniccomponent according to claim 6 or 7, wherein an electrically conductiveadhesive agent for forming a stress relaxation mechanism member isfurther formed on an upper face of said electrode.
 10. A stressrelaxation type circuit board on which an electronic component is to bemounted, wherein a stress relaxation mechanism member is disposed on asurface of said circuit board, said surface being on a side of aconnection portion where said circuit board is to be connected to saidelectronic component, and wherein a solderable layer is on a surface ofsaid stress relaxation mechanism member, said surface being on a sidewhere said stress relaxation mechanism member is connected to saidelectronic component.
 11. A stress relaxation type circuit boardaccording to claim 10, wherein said stress relaxation mechanism memberis electrically conductive.
 12. A stress relaxation type circuit boardaccording to claim 10 or 11, wherein said stress relaxation mechanismmember is disposed for each of electrodes which are on said connectionportion-side surface of said circuit board, in a manner that said stressrelaxation mechanism members are electrically separated from each other.13. A stress relaxation type circuit board according to claim 10 or 11,wherein plural sets of said electronic components are mounted on saidcircuit board.
 14. A stress relaxation type circuit board according toclaim 13, wherein said plural sets of electronic components havedifferent sizes or different shapes.
 15. A stress relaxation typecircuit board according to claim 10 or 11, wherein said solderable layerconsists of copper foil, or a metal which is formed by thermallydecomposing an organometallic complex film.
 16. A stress relaxation typecircuit board according to claim 10 or 11, wherein said stressrelaxation mechanism member is formed by an electrically conductiveadhesive agent.
 17. A stress relaxation type circuit board according toclaim 10 or 11, wherein said stress relaxation mechanism member isformed by a solderable electrically conductive adhesive agent.
 18. Astress relaxation type circuit board according to claim 10 or 11,wherein an electrode on said connection portion-side surface functionsalso as said stress relaxation mechanism member.
 19. A stress relaxationtype circuit board according to claim 10 or 11, wherein said electrodeis made of an electrically conductive resin composition.
 20. A stressrelaxation type circuit board according to claim 10 or 11, wherein saidelectrically conductive resin composition contains, as main components,at least an electrically conductive filler, a thermosetting resin, andexpandable hollow synthetic resin particles.
 21. A stress relaxationtype circuit board according to claim 10 or 11, wherein a solder layer,or an electrically conductive adhesive agent for forming a stressrelaxation mechanism member is further formed on an upper face of saidelectrode.
 22. A stress relaxation type electronic component mountedmember wherein an electronic component is mounted on a circuit board viaa stress relaxation mechanism member, said stress relaxation mechanismmember is electrically conductive, and wherein said stress relaxationmechanism member is configured by an electrically conductive adhesiveagent and a solder layer.
 23. A stress relaxation type electroniccomponent mounted member according to claim 22, wherein said stressrelaxation mechanism member is disposed for each of electrodes which arein said connection portion between said electronic component and saidcircuit board, in a manner that said stress relaxation mechanism membersare electrically separated from each other.
 24. A stress relaxation typeelectronic component mounted member according to claim 22 or 23, whereinsaid stress relaxation mechanism member functions also as an electrodedisposed on said electronic component and/or said circuit board.
 25. Astress relaxation type electronic component mounted member according toclaim 22 or 23, wherein said stress relaxation mechanism member isconfigured by an electrode made of an electrically conductive resincomposition disposed on said electronic component and/or said circuitboard, and at least one of an electrically conductive adhesive agent anda solder layer.
 26. A stress relaxation type electronic componentmounted member according to claim 22, wherein said electronic componentconsists of plural electronic components having different sizes ordifferent shapes.
 27. A stress relaxation type electronic componentmounted member according to claim 22, wherein said electricallyconductive adhesive agent and said solder layer are connected to eachother via a solderable layer.